Shim for disk brakes, and disk brake

ABSTRACT

A novel disc brake shim and a disc brake that can effectively suppress vibration and squeal are provided. The disc brake shim that is formed of a multilayer structure with three layers or more including at least a base material layer formed of a metal sheet, and a foamed rubber layer that is laminated on a main surface on one side of the base material layer, wherein the foamed rubber layer is an intermediate layer of the multilayer structure, and the disc brake including pad materials on both sides in an axial direction of a disc rotor, and shims on opposite sides from the disc rotor, of the pad materials adjacently, wherein each of the shims is the disc brake shim according to the present invention.

TECHNICAL FIELD

The present invention relates to a disc brake shim and a disc brake.

BACKGROUND ART

In general, disc brakes are widely used in automobiles and the like(refer to Patent Literature 1 (Japanese Patent Laid-Open No.2010-31960), for example).

FIG. 12 is a vertical sectional view in one exemplary mode of a discbrake. As illustrated in FIG. 12 , a disc brake B is structured suchthat it applies brakes by pressing brake pads 30 and 30 that arearranged on both sides in an axial direction of a disc rotor 60 thatrotates integrally with a wheel, with a pressing member 70 formed of apiston and the like by hydraulic pressure of a brake oil 80 in a caliper50, and pressing the brake pads 30 and 30 from both sides of the discrotor 60.

If the brake pad 30 is directly pressed to the disc rotor 60 by thepressing member 70 during braking as described above, a back metal 40 ofthe brake pad and the pressing member 70 relatively move, and each partof the brake vibrates due to frictional vibration or the like that isgenerated between the brake pad 30 and the disc rotor 60, so thatabnormal noise commonly referred to as squeal may occur.

CITATION LIST Patent Literature

-   [Patent Literature 1] Japanese Patent Laid-Open No. 2010-31960

SUMMARY OF INVENTION Technical Problem

In order to prevent occurrence of such squeal, a shim S is interposedbetween a pad material P formed of the brake pad 30 and the back metal40, and the pressing member 70, as illustrated in FIG. 12 and FIG. 13 .As the shim S, a rubber coat metal (RCM) with thin rubber layers 20 and20 fixed onto surfaces of a metal sheet 10 that is formed of a joinedmaterial in which a stainless steel sheet and an iron sheet are bondedtogether as illustrated in FIG. 12 and FIG. 13 , and it is consideredthat according to such a shim S, the vibration that is the cause ofsqueal can be dampened by using elasticity of the rubber layer 20 duringa braking time by pressing by the pressing member 70.

However, according to the study by the present inventors, even the shimformed of the above described rubber-coated metal (RCM) cannot alwayssufficiently satisfy the needs of automobile users for comfort andquietness during driving, which have been increasing more and more inrecent years, and therefore, there has been a demand for disc brakeshims that can even more suppress vibration and squeal.

Accordingly, an object of the present invention is to provide a noveldisc brake shim and disc brake that can effectively suppress vibrationand squeal.

Solution to Problem

As a result of earnest study conducted by the present inventors attainthe above described object, the present inventors has found that theabove described technical problem can be solved by a disc brake shimthat is formed of a multilayer structure with three layers or morehaving at least a base material layer formed of a metal sheet, and afoamed rubber layer that is laminated on a main surface on one side ofthe base material layer, wherein the foamed rubber layer is anintermediate layer of the multilayer structure, and have completed thepresent invention based on the present findings.

In other words, the present invention provides

-   (1) a disc brake shim that is formed of a multilayer structure with    three layers or more including at least a base material layer formed    of a metal sheet, and a foamed rubber layer that is laminated on a    main surface on one side of the base material layer, wherein the    foamed rubber layer is an intermediate layer of the multilayer    structure,-   (2) the disc brake shim as set forth in (1) described above, wherein    the foamed rubber layer is a foam of an unfoamed rubber layer having    a thickness of 15 to 100 μm with an expansion ratio of 2 to 4 times,-   (3) the disc brake shim as set forth in (1) or (2) described above,    wherein the foamed rubber layer is a foam of an unfoamed rubber    layer containing 20 to 70% by mass of polymer with a Mooney value of    10 to 70, and 20 to 60% by mass of a heat-decomposable chemical    foaming agent,-   (4) the disc brake shim as set forth in any one of (1) to (3)    described above, wherein the disc brake shim is a base shim or a    cover shim in a laminated shim in which the cover shim is laminated    on the base shim, and-   (5) a disc brake including pad materials on both sides in an axial    direction of a disc rotor, and shims on opposite sides from the disc    rotor, of the pad materials adjacently,

wherein each of the shims is the disc brake shim as set forth in any oneof (1) to (4) described above.

Advantageous Effect of Invention

According to the present invention, it is considered that not only thefoamed rubber layer provided on the base material layer hardly transmitsvibration of the brake pads and the like because the foamed rubber layerhas a low density with a foamed part, but also the foamed rubber layerdeforms to follow the vibration of the brake pads and the like to easilyconvert the vibration into thermal energy because the foamed rubberlayer has flexibility, and the foamed rubber layer can easily convertvibration of an external member into frictional heat because the foamedrubber layer further has a high friction coefficient.

Consequently, according to the present invention, it is possible toprovide a novel disc brake system and disc brake that can effectivelysuppress vibration and squeal.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a vertical sectional view showing an exemplary mode of a discbrake shim according to the present invention.

FIG. 2 is a vertical sectional view showing an exemplary mode of thedisc brake shim according to the present invention.

FIG. 3 is a vertical sectional view showing an exemplary mode of thedisc brake shim according to the present invention.

FIG. 4 is a vertical sectional view showing an exemplary mode of thedisc brake shim according to the present invention.

FIG. 5 is a vertical sectional view showing an exemplary mode of thedisc brake shim according to the present invention.

FIG. 6 is a vertical sectional view showing an exemplary mode of thedisc brake shim according to the present invention.

FIG. 7 is a vertical sectional view showing an exemplary mode of use ofthe disc brake shim according to the present invention.

FIG. 8 is a vertical sectional view showing an exemplary mode of use ofthe disc brake shim according to the present invention.

FIG. 9 is a vertical sectional view showing an exemplary mode of use ofthe disc brake shim according to the present invention.

FIG. 10 is a vertical sectional view showing an exemplary mode of use ofthe disc brake shim according to the present invention.

FIG. 11 is a vertical sectional view showing an exemplary mode of use ofthe disc brake shim according to the present invention.

FIG. 12 is a vertical sectional view showing a schematic structureexample of a disc brake.

FIG. 13 is a vertical sectional view showing an exemplary mode of use ofa disc brake shim that is an object to be compared.

FIG. 14 is a diagram showing vibration dampening property evaluation inan example and a comparative example of the present invention.

DESCRIPTION OF EMBODIMENTS

A disc brake shim according to the present invention is formed of amultilayer structure with three layers or more having at least a basematerial layer formed of a metal sheet, and a foamed rubber layer thatis laminated and disposed on a main surface on one side of the basematerial layer, wherein the foamed rubber layer is disposed as anintermediate layer of the multilayer structure.

In the present application documents, the disc brake shim means the onein a state in which respective adjacent layers forming the disc brakeshim are chemically or physically fixed.

In the disc brake shim according to the present invention, the metalsheet forming the base material layer is not particularly limited, butit is possible to cite sheet materials formed of a stainless steel(ferritic, martensitic, austenitic, and the like), iron, a platingmaterial, aluminum and the like, and a sheet material formed of astainless steel or iron is preferable.

In the disc brake shim according to the present invention, the metalsheet forming the base material layer may be formed by joining aplurality of metal sheets by pasting or the like, and as the metalsheet, a joined sheet of a stainless steel sheet and an iron sheet ispreferable.

In the disc brake shim according to the present invention, a thicknessof the metal sheet forming the base material layer is not particularlylimited, but is normally 0.4 to 0.8 mm.

In the disc brake shim according to the present invention, the foamedrubber layer is preferably a foam of an unfoamed rubber layer.

The foamed rubber layer is preferably a foam of an unfoamed rubber layerof a thickness of 15 to 100 μm, more preferably a foam of an unfoamedrubber layer of a thickness of 30 to 70 μm, and is even more preferablya foam of an unfoamed rubber layer of a thickness of 40 to 60 μm.

A thickness of the above described unfoamed rubber layer means anarithmetic mean value when thicknesses at ten spots are measured byusing a dial gauge.

In the disc brake shim according to the present invention, the thicknessof the unfoamed rubber layer is within the above described range, sothat the foamed rubber layer having a desired thickness can be easilyformed.

As the foamed rubber layer, an expansion ratio of an unfoamed rubberlayer is not particularly limited, but the foamed rubber layer ispreferably a foam that is 2 to 4 times as large as the unfoamed rubberlayer.

In the present application documents, the above described expansionratio means a value that is calculated by an expression below.

Expansion ratio=foamed rubber layer thickness/unfoamed rubber layerthickness

(Note that the thickness of the foamed rubber layer means the arithmeticmean value when the thicknesses at 10 spots are measured by using a dialgauge, and the thickness of the unfoamed rubber layer also means anarithmetic mean value when thicknesses at 10 spots are measured by usinga dial gauge.)

In the disc brake shim according to the present invention, the expansionratio of the unfoamed rubber layer is within the above described range,so that the foamed rubber layer having a desired thickness can be easilyformed.

The thickness of the foamed rubber layer is preferably 30 to 200 μm,more preferably 60 to 140 μm, and even more preferably 80 to 120 μm.

Since the thickness of the foamed rubber layer is within the abovedescribed range, it is possible to easily provide the disc brake shimhaving a desired density, and having a desired flexibility and frictioncoefficient.

A rubber composition forming the foamed rubber layer preferably containsa polymer (rubber component) having a Mooney value of 10 to 70, and morepreferably contains a polymer having a Mooney value of 20 to 60.

In the present application documents, the Mooney value means a valuethat is measured by a method specified in JIS K6300-1 by using MooneyViscometer SMV-201 made by Shimadzu Corporation.

When the Mooney value of the polymer is less than 10, deformation of thepolymer by blowing gas easily increases, and when the Mooney value ismore than 70 on the contrary, deformation of the polymer by blowing gaseasily becomes insufficient.

As the polymer, it is possible to cite one or more selected from nitrilerubber (NBR), hydrogenated nitrile rubber (HNBR), fluororubber, ethylenepropylene diene rubber (EPDM), acrylic rubber and the like, and one ormore selected from nitrile rubber (NBR), hydrogenated nitrile rubber(HNBR), and fluororubber is preferable.

Furthermore, as the above described nitrile rubber (NBR), in order togive oil resistance, a nitrile rubber with an AN value (content ofacrylonitrile group in NBR) of 39 to 52 is preferable, and a nitrilerubber with an AN value of 40 to 48 is more preferable.

Since the unfoamed robber layer contains the above described polymer, itis possible to easily obtain a foamed rubber layer having desiredproperties.

The unfoamed rubber layer preferably contains 10 to 70% by mass of theabove described polymer, more preferably 20 to 60% by mass of the abovedescribed polymer, and even more preferably 30 to 50% by mass of theabove described polymer.

The unfoamed rubber layer contains the above described polymer in theabove described ratio, and thereby it is possible to effectivelysuppress sagging of the foamed rubber layer due to compression duringbraking.

When the foamed rubber layer is a foam of an unfoamed rubber layer, suchan unfoamed rubber layer preferably contains a heat-decomposablechemical foaming agent.

As the heat-decomposable foaming agent, a heat-decomposable foamingagent with a foaming temperature of 120° C. or higher is preferable, anda heat-decomposable foaming agent with a foaming temperature of 150 to210° C. is more preferable.

As a heat-decomposable foaming agent, it is possible to cite one or moreselected from, for example, an azodicarbonamide foaming agent,dinitrosopentamethylene tetramine foaming agent,oxybisbenzenesulfonylhydrazide foaming agent, sodium bicarbonate foamingagent and the like.

The unfoamed rubber layer preferably contains 10 to 60% by mass of theabove described heat-decomposable chemical foaming agent, and morepreferably contains 15 to 35% by mass of the above describedheat-decomposable chemical foaming agent.

The unfoamed rubber layer contains the above described heat-decomposablechemical foaming agent in the above described ratio, and thereby it ispossible to easily form the foamed rubber layer having a desireddensity, and having a desired flexibility and friction coefficient.

Furthermore, the unfoamed rubber layer may contain a vulcanizing agentand a vulcanization accelerator. The vulcanizing agent is preferablycontained in a large amount so as to increase a vulcanization density,and in the case of sulfur vulcanization, a sulfur compound amount ispreferably 1.5 to 4.5 g (1.5 to 4.5 phr (parts per hundred rubber)) for100 gram of polymer that is a rubber component.

Furthermore, as the vulcanization accelerator, it is preferable to use ahigh-speed vulcanization accelerator that rises with a time to T50within 4 minutes according to curast data (150° C.). Note that the timeto T50 according to the curast data (150°) means a time required until avulcanization degree of rubber reaches T50 (elapsed time until reaching50% of maximum torque) when vulcanization is performed at 150° C. byusing a curast testing machine (JSR curast meter III made by NichigoShoji Co., Ltd.).

The foamed rubber layer preferably has a continuous foam rate of 60% ormore, and more preferably has a continuous foam rate of 80% or more.

In the present application documents, the continuous foam rate means avalue that is calculated by an expression below.

Note that “replaced water weight (g)” shown below means a valuecalculated by weight (g) after underwater replacement−weight (g) beforeunderwater replacement treatment when treatment of immersing the discbrake shim having the above described foamed layer according to thepresent invention in water and thereafter performing vacuum-deaerationof the disc brake shim is repeated a plurality of times until the weightafter underwater replacement becomes constant.

Furthermore, “volume of the foamed rubber layer” shown below means avalue obtained from a product of a foamed rubber layer thicknessobtained from an arithmetic mean value of thickness at 10 spots by usinga dial gauge, and a surface area.

Furthermore, “volume of the unfoamed rubber layer” also means a valueobtained from a product of an unfoamed rubber layer thickness obtainedfrom an arithmetic mean value of the thicknesses at 10 spots by using adial gauge, and a surface area.

Continuous foam rate (%)={replaced water weight (g)/(foamed rubber layervolume (cm³)−volume of rubber layer before foaming) (cm^(3)}×)100

The continuous foam rate is within the above described range, andthereby it is possible to easily obtain a foamed rubber layer having adesired density, and having a desired flexibility and frictioncoefficient.

In the disc brake shim according to the present invention, it ispossible to form the foamed rubber layer by, for example, dissolving arubber compound containing respective desired amounts of polymer and aheat-decomposable chemical foaming agent in an organic solvent toprepare a coating liquid, applying the coating liquid to a metal sheetto be the base material layer, and fixing the coating liquid.

The above described organic solvent is not limited as long as it candissolve the above described rubber compound, but it is preferable touse an organic solvent prepared by mixing an ester solvent in a ratio of10 to 90% by mass with respect to 10 to 90% by mass of aromatichydrocarbon solvent (ketone type is also possible) such as toluene.Furthermore, as the coating liquid, a coating liquid that is prepared bydissolving the above described rubber compound in the above describedorganic solvent so that the solid content concentration is 10 to 60% bymass is preferable.

A coating method of the coating liquid containing the rubber compound isnot particularly limited, but the coating liquid is preferably coated bya skimmer coater, a roll coater or the like that can control a coatingthickness.

After the coating liquid is applied, thermal treatment is preferablyperformed at 150 to 260° C. for 5 to 15 minutes to foam the foamingagent, and a foamed rubber layer is fixed while being formed. At thistime, foaming conditions such as a vulcanizing agent and the foamingagent to be used, a heating time and the like are adjusted so that theexpansion ratio and the continuous foam rate of the foamed rubber layerto be obtained have desired values.

The expansion ratio can be easily controlled by adjusting types andcompound ratios of the polymer having the above described Mooney value,and the vulcanizing agent and the foaming agent described above, and canbe easily controlled in particular by adjusting the Mooney value and avulcanizing rate of the polymer.

When the vulcanizing rate is increased, vulcanization advances beforethe polymer expands and deforms by blowing gas, and therefore, theexpansion rate is easily suppressed. When the vulcanizing rate isdecreased on the contrary, deformation of the polymer by blowing gastakes precedence over a rubber curing rate by vulcanization, andtherefore the expansion ratio easily increases.

For example, when a polymer with a Mooney value of 20 to 40, avulcanization accelerator at a low rate (curast data: a rising time toT50 in vulcanization at 150° C. is around 5 to 6 minutes), and a foamingagent with a low foam decomposition temperature are combined, theexpansion ratio increases, and when a polymer with a Mooney value of 40to 60, a vulcanization accelerator with a high vulcanization rate(curast data: a rising time to T50 in vulcanization at 150° C. is around1 to 3 minutes), and a foaming agent with a high foam decompositiontemperature are combined on the contrary, the expansion ratio is easilydecreased.

In this way, by combination of the polymer, vulcanization acceleratorand foaming agent, it is possible to arbitrarily control the expansionratio.

The disc brake shim according to the present invention is formed of amultilayer structure with three layers or more having at least a basematerial layer formed of a metal sheet, and a foamed rubber layer thatis laminated and disposed on a main surface on one side of the basematerial layer, wherein the foamed rubber layer is disposed as anintermediate layer of the multilayer structure.

The disc brake shim according to the present invention is formed of amultilayer structure with three layers or more, wherein the foamedrubber layer is disposed as an intermediate layer. Here, theintermediate layer means a layer that is located on any one of locationson an inner side except for outermost layers, among a plurality ofconstituent layers that are three layers or more.

The disc brake shim according to the present invention may have anadhesive layer, in addition to the base material layer formed of a metalsheet, and the foamed rubber layer that is laminated and disposed on themain surface on one side of the base material layer.

As an adhesive forming the adhesive layer, it is possible to cite one ormore selected from an acrylic adhesive, silicon adhesive, rubberadhesive, urethane adhesive and the like, and one or more selected froman acrylic adhesive and silicon adhesive is more preferable.

When the adhesive is an acrylic adhesive, one or more selected from ametal chelate crosslinking agent, isocyanate crosslinking agent, epoxycrosslinking agent and the like is preferably further used as acrosslinking agent.

The disc brake shim according to the present invention has the adhesivelayer, and thereby can produce an excellent ability to prevent squeal byan excellent vibration control effect of the adhesive.

FIG. 1 is a vertical sectional view showing an exemplary mode of a discbrake shim according to the present invention having an adhesive layer.

FIG. 1 is a vertical sectional view showing the exemplary mode of a discbrake shim S that is formed of a multilayer structure with a threelayers having a base material layer 1 formed of a metal sheet, a foamedrubber layer 2 that is laminated on a main surface on one side of thebase material layer, and an adhesive layer “a” that is laminated on amain surface on an opposite side from the base material layer 1, of thefoamed rubber layer 2, and as shown in FIG. 1 , the disc brake shim Saccording to the present exemplary mode has the base material layer 1and the adhesive layer “a” as outermost layers, and has the foamedrubber layer 2 as an intermediate layer between the base material layer1 and the adhesive layer “a”.

In the present exemplary mode, in a braking time, the disc brake shim Sis pressed (in a lower direction from an upper side in FIG. 1 ) by apressing member such as a piston that is provided in a caliper, and itis considered that not only the foamed rubber layer 2 forming the discbrake shim S hardly transmits vibration of the brake pad 3 and the likebecause the foamed rubber layer 2 has a low density with a foamed part,but also the foamed rubber layer 2 deforms to follow the vibration ofthe brake pad 3 and the like to easily convert the vibration intothermal energy because the foamed rubber layer 2 has flexibility.

Consequently, according to the disc brake shim according to the presentinvention shown in FIG. 1 , it is possible to effectively suppressvibration and squeal.

The disc brake shim according to the present invention may have a solidrubber layer, in addition to the base material layer formed of a metalsheet, and the foamed rubber layer that is laminated and disposed on themain surface on one side of the base material layer.

In the present application documents, the solid rubber layer means arubber layer that is formed without going through a foaming step by afoaming agent and has no air bubbles (derived from a foaming agent).

A thickness of the solid rubber layer is preferably 25 to 250 μm, morepreferably 50 to 200 μm, and even more preferably 100 to 180 μm.

The thickness of the above described solid rubber layer means anarithmetic mean value at a time of measuring thicknesses at 10 spots byusing a dial gauge.

As a polymer (rubber component) forming the solid rubber layer, one ormore selected from nitrile rubber (NBR), hydrogenated nitrile rubber(HNBR), fluororubber, ethylene propylene diene rubber (EPDM) and acrylicrubber, and the like, and one or more selected from nitrile rubber(NBR), hydrogenated nitrile rubber (HNBR), and fluororubber ispreferable.

Furthermore, as the above described nitrile rubber (NBR), in order togive oil resistance, a nitrile rubber with an AN value (content ofacrylonitrile group in NBR) of 25 to 50 is preferable, and a nitrilerubber with an AN value of 30 to 45 is more preferable.

Furthermore, the solid rubber layer may contain a vulcanizing agent anda vulcanization accelerator. The vulcanizing agent is preferablycontained in a large amount so as to increase a vulcanization density,and in the case of sulfur vulcanization, a sulfur compound amount ispreferably 1.5 to 4.5 g (1.5 to 4.5 phr (parts per hundred rubber)) for100 gram of polymer that is a rubber component.

Furthermore, as the vulcanization accelerator, it is preferable to use avulcanization accelerator at a high rate with a time to T50 risingwithin 4 minutes according to curast data (150° C.).

In the disc brake shim according to the present invention, it ispossible to form the solid rubber layer by, for example, dissolving arubber compound containing a desired amount of polymer in an organicsolvent to prepare a coating liquid, applying the coating liquid to anobject to be coated such as the base material layer, and fixing thecoating liquid.

The organic solvent is not limited as long as it can dissolve the abovedescribed rubber compound, but it is preferable to use an organicsolvent prepared by mixing an ester solvent in a ratio of 10 to 90% bymass with respect to 10 to 90% by mass of aromatic hydrocarbon solvent(ketone type is also possible) such as toluene. Furthermore, as thecoating liquid, a coating liquid that is prepared by dissolving theabove described rubber compound in the above described organic solventso that the solid content concentration is 10 to 60% by mass ispreferable.

A coating method of the coating liquid containing the rubber compound isnot particularly limited, but the coating liquid is preferably coated bya skimmer coater, a roll coater or the like that can control a coatingthickness.

FIG. 2 is a vertical sectional view showing an exemplary mode of a discbrake shim S in which a solid rubber layer 20 is further laminated on amain surface on an opposite side from the foamed rubber layer 2, of thebase material layer 1, in the exemplary mode shown in FIG. 1 .

As shown in FIG. 2 , in the present exemplary mode, the disc brake shimS is formed of a multilayered structure with four layers in which thesolid rubber layer 20, the base material layer 1, the foamed rubberlayer 2 and an adhesive layer “a” are sequentially laminated, and arefixed, and has the foamed rubber layer 2 as an intermediate layerbetween the base material layer 1 and the adhesive layer “a”.

In the present exemplary mode, in a braking time, the disc brake shim Sis also pressed (in a lower direction from an upper side in FIG. 2 ) bya pressing member such as a piston that is provided in a caliper, and itis also considered that not only the foamed rubber layer 2 forming thedisc brake shim S hardly transmits vibration of the brake pad 3 and thelike because the foamed rubber layer 2 has a low density with a foamedpart, but also the foamed rubber layer 2 deforms to follow the vibrationof the brake pad 3 and the like to easily convert the vibration intothermal energy because the foamed rubber layer 2 has flexibility, andthe foamed rubber layer 2 can easily convert the vibration of the brakepad 3 and the like into frictional heat because the foamed rubber layer2 further has a high friction coefficient.

The disc brake shim S according to the exemplary mode shown in FIG. 2further has the solid rubber layer 20 and therefore, can suppressvibration and squeal more, as compared with the disc brake shim Saccording to the exemplary mode shown in FIG. 1 .

The disc brake shim according to the present invention may have aplurality of base material layers each formed of a metal sheet.

The disc brake shim according to the present invention more easilyimproves vibration control performance as a constraint vibration controlstructure, by having the plurality of base material layers each formedof a metal sheet.

In this case, as the metal sheet forming the plurality of base materiallayers respectively, same metal sheet as the aforementioned metal sheetcan be cited.

FIG. 3 is a vertical sectional view showing an exemplary mode of a discbrake shim S in which a base material layer 1 formed of a metal sheet isfurther laminated on the main surface on an opposite side from thefoamed rubber layer 2, of the adhesive layer “a”, in the exemplary modeshown in FIG. 2 .

As shown in FIG. 3 , in the present exemplary mode, the disc brake shimS is formed of a multilayer structure with five layers in which a solidrubber layer 20, an upper side base material layer 1 formed of a metalsheet, the foamed rubber layer 2, the adhesive layer “a” and a lowerside base material layer 1 formed of a metal sheet are sequentiallylaminated in this order (in a lower direction from an upper part in FIG.3 ), and are fixed, and has the foamed rubber layer 2 as an intermediatelayer between the upper side base material layer 1 and the adhesivelayer “a”.

In the present exemplary mode, in a braking time, the disc brake shim Sis also pressed (in the lower direction from an upper side in FIG. 3 )by a pressing member such as a piston that is provided in a caliper, andit is also considered that not only the foamed rubber layer 2 formingthe disc brake shim S hardly transmits vibration of a brake pad 3 andthe like because the foamed rubber layer 2 has a low density with afoamed part, but also the foamed rubber layer 2 deforms to follow thevibration of the brake pad 3 and the like to easily convert thevibration into thermal energy because the foamed rubber layer 2 hasflexibility.

The disc brake shim S according to the exemplary mode shown in FIG. 3further has the base material layer 1, and therefore can suppressvibration and squeal more, as compared with the disc brake shim Saccording to the exemplary mode shown in FIG. 2 .

FIG. 4 is a vertical sectional view of a disc brake shim S according toanother mode of the present invention.

The disc brake shim S shown in FIG. 4 is formed of a multilayerstructure with five layers in which an upper side base material layer 1formed of a metal sheet, an adhesive layer “a”, a foamed rubber layer 2,a lower side base material layer 1 formed of a metal sheet and a solidrubber layer 20 are sequentially laminated in this order (in a lowerdirection from an upper part in FIG. 4 ), and are fixed, and has thefoamed rubber layer 2 as an intermediate layer between the lower sidebase material layer 1 and the adhesive layer “a”.

In the present exemplary mode, in a braking time, the disc brake shim Sis also pressed (in the lower direction from an upper side in FIG. 4 )by a pressing member such as a piston that is provided in a caliper, andit is also considered that not only the foamed rubber layer 2 formingthe disc brake shim S hardly transmits vibration of a brake pad 3 andthe like because the foamed rubber layer 2 has a low density with afoamed part, but also the foamed rubber layer 2 deforms to follow thevibration of the brake pad 3 and the like to easily convert thevibration into thermal energy because the foamed rubber layer 2 hasflexibility.

The disc brake shim S according to the exemplary mode shown in FIG. 4further has the solid rubber layer 20 and the plurality of base materiallayers 1, and therefore can suppress vibration and squeal more, ascompared with the disc brake shim S according to the exemplary modeshown in FIG. 1 .

FIG. 5 is a vertical sectional view of a disc brake shim S according toanother mode of the present invention.

The disc brake shim S shown in FIG. 5 is formed of a multilayerstructure with six layers in which an upper side solid rubber layer 20,an upper side base material layer 1 formed of a metal sheet, an adhesivelayer “a”, a foamed rubber layer 2, a lower side base material layer 1formed of a metal sheet and a lower side solid rubber layer 20 aresequentially laminated n this order (in a lower direction from an upperpart in FIG. 5 ), and are fixed, and has the foamed rubber layer 2 as anintermediate layer between the lower side base material layer 1 and theadhesive layer “a”.

In the present exemplary mode, in a braking time, the disc brake shim Sis also pressed (in the lower direction from an upper side in FIG. 5 )by a pressing member such as a piston that is provided in a caliper, andit is also considered that not only the foamed rubber layer 2 formingthe disc brake shim S hardly transmits vibration of a brake pad 3 andthe like because the foamed rubber layer 2 has a low density with afoamed part, but also the foamed rubber layer 2 deforms to follow thevibration of the brake pad 3 and the like to easily convert thevibration into thermal energy because the foamed rubber layer 2 hasflexibility.

The disc brake shim S according to the exemplary mode shown in FIG. 5further has the upper side solid rubber layer 20, and therefore cansuppress vibration and squeal more, as compared with the disc brake shimS according to the exemplary mode shown in FIG. 4 .

FIG. 6 is a vertical sectional view of a disc brake shim S according toanother mode of the present invention.

The disc brake shim S shown in FIG. 6 is formed of a multilayerstructure with six layers in which an upper side solid rubber layer 20,an upper side base material layer 1 formed of a metal sheet, a foamedrubber layer 2, an adhesive layer “a”, a lower side base material layer1 formed of a metal sheet and a lower side solid rubber layer 20 aresequentially laminated in this order (in a lower direction from an upperpart in FIG. 6 ), and are fixed, and has the foamed rubber layer 2 as anintermediate layer between the upper side base material layer 1 and theadhesive layer “a”.

In the present exemplary mode, in a braking time, the disc brake shim Sis also pressed (in the lower direction from an upper side in FIG. 6 )by a pressing member such as a piston that is provided in a caliper, andit is also considered that not only the foamed rubber layer 2 formingthe disc brake shim S hardly transmits vibration of the brake pad 3 andthe like because the foamed rubber layer 2 has a low density with afoamed part, but also the foamed rubber layer 2 deforms to follow thevibration of the brake pad 3 and the like to easily convert thevibration into thermal energy because the foamed rubber layer 2 hasflexibility.

The disc brake shim S according to the exemplary mode shown in FIG. 6further has the lower side solid rubber layer 20, and therefore cansuppress vibration and squeal more, as compared with the disc brake shimS according to the exemplary mode shown in FIG. 3 .

The disc brake shim according to the present invention may be a baseshim or a cover shim, in a laminated shim in which the cover shim islaminated and disposed on the base shim.

For example, the disc brake shim according to the present invention maybe a base shim BS or a cover shim CS in a laminated shim MS in which thecover shim CS is laminated on the base shim BS, in a vertical sectionalview showing an outline of an exemplary mode of use of a disc brake shimaccording to the present invention illustrated in FIG. 7 .

In this case, only either one of the base shim and the cover shimforming the laminated shim may be the disc brake shim according to thepresent invention, or both of the base shim and the cover shim that formthe laminated shim may be the disc brake shim according to the presentinvention.

Note that in the present application documents, the base shim that formsthe laminated shim means a shim that is attached on a pad material sideat the time of arrangement, and the cover shim that forms the laminatedshim means a shim that is disposed on a pressing member side at the timeof arrangement. Furthermore, in the present application documents, thecover shim and the base shim means the cover shim and the base shim thatare in a state in which entire joined surfaces of both of them are notchemically or physically fixed, but in a state in which they areadjacent disposed.

When only the base shim that forms the laminated shim is the disc brakeshim according to the present invention, the structure of the cover shimcan be properly selected from the conventionally known cover shims, andis not particularly limited.

For example, as illustrated in FIG. 8 , a base shim BS that forms alaminated shim is the disc brake shim according to the presentinvention, and as a cover shim CS, a cover shim that is formed of a basematerial layer 1 formed of a metal sheet can be cited.

Furthermore, as illustrated in each of FIG. 9 and FIG. 10 , a base shimBS that forms a laminated shim is the disc brake shim according to thepresent invention, and as a cover shim CS, a cover shim in which a solidrubber layer 20 is laminated and fixed onto a main surface on one sideof a base material layer 1 formed of a metal sheet can be cited.

Furthermore, as illustrated in FIG. 11 , a base system BS forming alaminated shim is the disc brake shim according to the presentinvention, and as a cover shim CS, it is possible to cite a cover shimin which solid rubber layers 20 and 20 are respectively laminated andfixed onto main surface on both sides of a base material layer 1 formedof a metal sheet.

As the base material layers formed of the metal sheets and the solidrubber layers of the above described cover shims, it is possible to citethe base material layer and the solid rubber layer that are same asdescribed above respectively.

According to the present invention, it is considered that not only thefoamed rubber layer provided on the base material layer hardly transmitsvibration of a brake pad and the like because the foamed rubber layerhas a low density with a foamed part, but also the foamed rubber layerdeforms to follow vibration of the brake pad and the like to easilyconvert the vibration into thermal energy because the foamed rubberlayer has flexibility, and the foamed rubber layer can easily convertvibration of the outer member into a frictional heat because the foamedrubber layer has a high friction coefficient.

Consequently, according to the present invention, it is possible toprovide a novel disc brake shim that can effectively suppress vibrationand squeal.

Next, a disc brake according to the present invention will be described.

The disc brake according to the present invention is a disc brake havingpad materials disposed on both sides in an axial direction of a discrotor, and shims that are adjacent disposed on opposite sides from thedisc rotor, of the pad materials, wherein each of the shims is the discbrake shim according to the present invention.

As the disc rotor according to the present invention, a disc rotorhaving a mode as shown in FIG. 12 can be illustrated.

A disc brake B illustrated in FIG. 12 is a disc brake having brake pads30 and 30 that are arranged on both sides in an axial direction of adisc rotor 60 that rotates integrally with a wheel, and shims S and Sthat are adjacent on opposite sides from the disc rotor 60, of the padmaterials 30 and 30, and at least one of the above described shims S andS is the disc brake shim according to the present invention.

The disc brake B illustrated in FIG. 12 is structured such that itapplies brakes by pressing the brake pads 30 and 30 that are arranged onboth sides in the axial direction of the disc rotor 60 that rotatesintegrally with a wheel with a pressing member 70 formed of a piston andthe like by hydraulic pressure of a brake oil 80 in a caliper 50, andpressing the brake pads 30 and 30 from both sides of the disc rotor 60.

In the disc brake according to the present invention, details of thedisc brake shim are as described above.

Furthermore, in the disc brake according to the present invention, asspecific examples of the other component members such as the disc rotor,and the brake pads, conventionally known component members can be cited,and the other component members are not particularly limited.

According to the present invention, it is considered that not only thefoamed rubber layer forming the disc brake shim hardly transmitsvibration of a brake pad and the like because the foamed rubber layerhas a low density with a foamed part, but also the foamed rubber layerdeforms to follow vibration of the brake pad and the like to easilyconvert the vibration into thermal energy because the foamed rubberlayer has flexibility, and furthermore, the foamed rubber layer caneasily convert vibration of the outer member into a frictional heatbecause the foamed rubber layer has a high friction coefficient.

Consequently, according to the present invention, it is possible toprovide a novel disc brake that can effectively suppress vibration andsqueal.

Next, the present invention will be described more specifically byciting examples, but these examples are only illustrations, and do notintend to restrict the present invention.

EXAMPLE 1

A rubber compound formed from components shown in Table 1, andcompounded to have 50% by mass of a polymer, 25% by mass of a foamingagent, a total of 3% by mass of a vulcanizing agent and a vulcanizationaccelerator, and 22% by mass of a filler was dissolved in a mixed liquidof toluene and ethyl acetate (toluene:ethyl acetate=70:30 in a volumeratio) so as to have 40% by mass of a solid content concentration toprepare a coating liquid.

Subsequently, the above described coating liquid was applied onto theentire main surface on one side of the base material formed of astainless steel sheet (SUS sheet) with a thickness of 0.5 mm to have athickness of 125 μm by using a roll coater to fix and form an unfoamedrubber layer, and thereafter thermal treatment was applied thereto at210° C. for 10 minutes, whereby a foamed rubber layer with a thicknessof 100 μm was formed on the main surface on one side of the basematerial formed of an SUS sheet, and the laminated base material 1 wasobtained.

A solid rubber (acrylonitrile butadiene rubber (NBR) system) layer wasformed so as to have a thickness of 100 μm on the entire main surface onone side of the base material formed of a sheet material of a steel witha thickness of 0.4 mm, an adhesive layer was formed by coating to have athickness of 100 μm on the main surface on the other side, and thelaminated base material 2 was obtained.

By bonding the adhesive layer of the above described laminated basematerial 2 onto the foamed rubber layer of the above described laminatedbase material 1, a disc brake shim material was produced, which wasformed of a multilayer structure with five layers in which the upperside base material layer formed of a steel sheet material, a foamedrubber layer, an adhesive layer, the lower side base material layerformed of a steel sheet material and the solid rubber layer weresequentially laminated and disposed in this order from the upper side tothe lower side, and were fixed, and had the foamed rubber layer as anintermediate layer between the upper side base material layer and theadhesive layer.

The obtained disc brake shim material was provided for measurement ofvibration dampening property evaluation as follows, as a test piece.

<Vibration Dampening Property Evaluation>

In the state in which the obtained disc brake shim material was set sothat the solid rubber layer abuts on a support stand of a stainlesssteel sheet with a thickness of 5 mm of a loss coefficient measuringdevice (MS18143 made by Bruel & Kjar Sound & Vibration Measurement A/S),a loss coefficient η was measured under the conditions described belowin conformity with the central exciting method (constrained steel sheetmethod) specified in JIS G0602.

Results are shown in Table 2 and FIG. 14 .

Note that the higher the loss coefficient η, the higher the vibrationdampening properties.

(Measurement Conditions)

-   Temperature range: −20° C. to 15° C.-   Loss coefficient calculation method: antiresonance point half width    method-   Mode: secondary-   Tightening torque: 4 N·m

COMPARATIVE EXAMPLE 1

A rubber compound formed from the components shown in Table 1, andcompounded to contain 40% by mass of a polymer, a total of 3% by mass ofa vulcanizing agent and a vulcanization accelerator, and 57% by mass ofa filler was dissolved in a mixed liquid of toluene and ethyl acetate(toluene:ethyl acetate=70:30 in a volume ratio) so as to have 40% bymass of a solid content concentration to prepare a coating liquid.

Subsequently, the above described coating liquid was applied onto theentire main surface on one side of the base material formed of astainless steel sheet (SUS sheet) with a thickness of 0.5 mm to have athickness of 250 μm by using a roll coater, and thereafter, thermaltreatment was applied at 200° C. for 10 minutes, whereby a solid rubberlayer with a thickness of 100 μm was formed on the main surface on oneside of the base material formed of an SUS sheet, and the laminated basematerial 1 was obtained.

A solid rubber (acrylonitrile butadiene rubber (NBR) system) layer wasformed so as to have a thickness of 100 μm on the entire main surface onone side of the base material formed of a sheet material of a steel witha thickness of 0.4 mm, an adhesive layer was formed by coating to have athickness of 100 μm on the main surface on the other side, and thelaminated base material 2 was obtained.

By bonding the adhesive layer of the above described laminated basematerial 2 onto the solid rubber layer of the above described laminatedbase material 1, a disc brake shim material was produced, which wasformed of a multilayer structure with five layers in which the upperside base material layer formed of a steel sheet material, the upperside solid rubber layer, the adhesive layer, the lower side basematerial layer formed of a steel sheet material and the lower side solidrubber layer are sequentially laminated and disposed in this order fromthe upper side to the lower side, and are fixed, and had the solidrubber layer as an intermediate layer between the upper side basematerial layer and the adhesive layer.

The obtained disc brake shim material was provided for the followingvibration dampening property evaluation, as a test piece.

<Vibration Dampening Property Evaluation>

A loss coefficient η was measured under the same conditions as inexample 1, except that the obtained disc brake shim material wasoriented so that the lower side solid rubber layer abuts on the supportstand of a stainless steel sheet with a thickness of 5 mm of the losscoefficient measuring device (MS18143 made by Bruel & Kjar Sound &Vibration Measurement A/S).

Results are shown in Table 2 and FIG. 14 .

TABLE 1 Rubber compound component Rubber layer Rubber layer Polymerthickness thickness (rubber component) Vulca- Vulca- (μm) (μm)Continuous AN Mooney Foaming nizing nization (before Expansion (afterfoam rate Type value value agent agent accelerator heating) ratioheating) (%) Example 1 Acrylonitrile 33 50 Heat- Sulfur Sulfenamide 50 2100 100 butadiene decomposable system rubber (azodicarbonamide (NBR)system) Comparative Acrylonitrile 43 80 — Sulfur Thiazole 100 — 100 —example 1 butadiene system rubber (NBR)

TABLE 2 Comparative example 1 Example 1 Temperature (° C.) Losscoefficient η (−) Loss coefficient η (−) −20 0.0036 0.0045 −15 0.00550.0080 −10 0.0093 0.0169 −5 0.0179 0.0383 0 0.0374 0.0852 5 0.07580.1590 10 0.1606 0.2490 15 0.2827 0.3254

EXAMPLE 2 TO EXAMPLE 4

The disc brake shim materials were obtained, each of which was formed ofa multilayer structure with five layers in which the upper side basematerial layer formed of a steel sheet material, the foamed rubberlayer, the adhesive layer, the lower side base material layer formed ofa steel sheet material and a solid rubber layer were sequentiallylaminated in this other from the upper side to the lower side, and werefixed, and had the foamed rubber layer as an intermediate layer betweenthe upper side base material layer and the adhesive layer, in the sameway as in example 1, except that the content ratios of the foamingagents in the coating liquids were respectively changed to 10% by mass,and thereafter, the stainless steel sheet (SUS sheet) with a thicknessof 0.5 mm was changed to a cold-rolled steel sheet (SPCC) with athickness of 0.4 mm (example 2), was changed to a cold-rolled steelsheet (SPCC) with a thickness of 0.6 mm (example 3), and was changed toa cold-rolled steel sheet with a thickness of 0.8 mm (example 4), inexample 1.

The obtained disc brake shim materials were provided for the vibrationdampening property evaluation in the same way as in example 1, as thetest pieces, and peak values (maximum values) of the loss coefficients ηwere obtained.

As a result, the peak values (maximum values) of the loss coefficients ηwere respectively 0.0240 (example 2), 0.0390 (example 3), and 0.0570(example 4).

EXAMPLE 5 AND EXAMPLE 6

The disc brake shim materials were obtained, each of which was formed ofa multilayer structure with five layers in which the upper side basematerial layer formed of a steel sheet material, the foamed rubberlayer, the adhesive layer, the lower side base material layer formed ofa steel sheet material and the solid rubber layer were sequentiallylaminated in this other from the upper side to the lower side, and werefixed, and had the foamed rubber layer as an intermediate layer betweenthe upper side base material layer and the adhesive layer, in the sameway as in example 1, except that the content ratios of the foamingagents in the coating liquids were respectively changed to 10% by mass,and thereafter, the SUS sheet with a thickness of 0.5 mm was changed toa hot-dip zinc-coated steel sheet (SGCH) with a thickness of 0.4 mm(example 5), and was changed to a stainless steel sheet (SUS 301) with athickness of 0.4 mm (example 6), in example 1.

The obtained disc brake shim materials were provided for the vibrationdampening property evaluation in the same way as in example 1, as thetest pieces, and peak values (maximum values) of the loss coefficients ηwere obtained.

As a result, the peak values (maximum values) of the loss coefficients ηwere respectively 0.0270 (example 5), and 0.0330 (example 6).

Results of example 2 to example 6 are shown in Table 3.

TABLE 3 Steel sheet Peak value thickness of loss Steel sheet type (mm)coefficient η(−) Example 2 Cold-rolled steel sheet 0.4 0.0240 Example 3Cold-rolled steel sheet 0.6 0.0390 Example 4 Cold-rolled steel sheet 0.80.0570 Example 5 Hot-dip zinc-coated 0.4 0.0270 steel sheet Example 6Stainless steel sheet 0.4 0.0330 (SUS301)

EXAMPLE 7 TO EXAMPLE 9

The disc brake shim materials were obtained, each of which was formed ofa multilayer structure with five layers in which the upper side basematerial layer formed of a steel sheet material, the foamed rubberlayer, the adhesive layer, the lower side base material layer formed ofa steel sheet material and the solid rubber layer were sequentiallylaminated in this order from the upper side to the lower side, and werefixed, and had the foamed rubber layer as an intermediate layer betweenthe upper side base material layer and the adhesive layer, in the sameway as in example 1, except that after the content ratios of the foamingagents in the coating liquids were respectively changed to 10% by mass,and the stainless steel sheet (SUS sheet) with a thickness of 0.5 mm waschanged to a cold-rolled steel sheet (SPCC) with a thickness of 0.4 mm,the foamed rubber layer with a thickness of 30 μm was obtained bythermally treating the unfoamed rubber layer with a thickness of 15 μm(example 7), the foamed rubber layer with a thickness of 100 μm wasobtained by thermally treating the unfoamed rubber layer with athickness of 50 μm (example 8), and the foamed rubber layer with athickness of 200 μm was obtained by thermally treating the unfoamedrubber layer with a thickness of 100 μm (example 9), in example 1.

The obtained respective disc brake shim materials were provided for thevibration dampening property evaluation in the same way as in example 1,as the test pieces, and peak values (maximum values) of the losscoefficients η were obtained.

As a result, the peak values (maximum values) of the loss coefficients ηwere respectively 0.0330 (example 7), 0.0240 (example 8), and 0.0210(example 9).

EXAMPLE 10 AND EXAMPLE 11

The disc brake shim materials were obtained, each of which was formed ofthe multilayer structure with five layers in which the upper side basematerial layer formed of a steel sheet material, the foamed rubberlayer, the adhesive layer, the lower side base material layer formed ofa steel sheet material and the solid rubber layer were sequentiallylaminated in this order from the upper side to the lower side, and werefixed, and had the foamed rubber layer as an intermediate layer betweenthe upper side base material layer and the adhesive layer, in the sameway as in example 1, except that after the stainless steel sheet (SUSsheet) with a thickness of 0.5 mm was changed to a cold-rolled steelsheet (SPCC) with a thickness of 0.4 mm, the content ratio of thefoaming agent in the coating liquid was changed to 20% by mass (example10), and the content ratio of the foaming agent in the coating liquidwas changed to 30% by mass (example 11) in example 1.

The obtained disc brake shim materials were provided for the vibrationdampening property evaluation in the same way as in example 1, as thetest pieces, and peak values (maximum values) of the loss coefficients ηwere obtained.

As a result, the peak values (maximum values) of the loss coefficients ηwere respectively 0.0400 (example 10), and 0.0330 (example 11).

Results of example 7 to example 11 are shown in Table 4.

TABLE 4 Foamed Foaming agent rubber content ratio Peak value Steel sheetlayer in coating of loss Steel sheet thickness thickness liquidcoefficient type (mm) (mm) (% by mass) η(−) Example 7 Cold-rolled 0.4 3010 0.0330 steel sheet Example 8 Cold-rolled 0.4 100 10 0.0240 steelsheet Example 9 Cold-rolled 0.4 200 10 0.0210 steel sheet Example 10Cold-rolled 0.4 100 20 0.0400 steel sheet Example 11 Cold-rolled 0.4 10030 0.0330 steel sheet

According to the results of example 1 to example 11, it is found thatthe disc brake shim according to the present invention is formed of amultilayer structure with three layers or more having the base materiallayer formed of a metal sheet, and the foamed rubber layer that islaminated on the main surface on one side of the base material layer,wherein the above described foamed rubber layer is the intermediatelayer in the above described multilayer structure, and thereby in therange of all temperatures of measurement, the loss coefficients are high(example 1 and example 2) or the peak values of the loss coefficientsare 0.0200 or more which are high (example 3 to example 12), so that thedisc brake shim of the present invention exhibits excellent brakingperformance under these temperatures, and can favorably suppressoccurrence of squeal.

In contrast to the above, according to the results of comparativeexample 1, it is found that in the disc brake shim having the solidrubber layer instead of the foamed rubber layer, the loss coefficientsare low in the range of all the temperatures of measurement, so thatunder these temperatures, the disc brake shim is inferior in brakingperformance, and cannot suppress occurrence of squeal.

INDUSTRIAL APPLICABILITY

According to the present invention, it is possible to provide a noveldisc brake shim and disc brake that can effectively suppress vibrationand squeal.

REFERENCE SIGNS LIST

-   1 base material layer-   2 foamed rubber layer-   3 brake pad-   4 back metal-   10 base material layer-   20 solid rubber layer-   30 brake pad-   40 back metal-   50 caliper-   60 disc rotor-   70 pressing member-   80 brake oil-   a adhesive layer-   S disc brake shim-   P pad material-   MS laminated shim-   CS cover shim-   BS base shim

1. A disc brake shim that is formed of a multilayer structure with threelayers or more including at least a base material layer formed of ametal sheet, and a foamed rubber layer that is laminated on a mainsurface on one side of the base material layer, wherein the foamedrubber layer is an intermediate layer of the multilayer structure. 2.The disc brake shim according to claim 1, wherein the foamed rubberlayer is a foam of an unfoamed rubber layer having a thickness of 15 to100 μm with an expansion ratio of 2 to 4 times.
 3. The disc brake shimaccording to claim 1, wherein the foamed rubber layer is a foam of anunfoamed rubber layer containing 20 to 70% by mass of polymer with aMooney value of 10 to 70, and 20 to 60% by mass of a heat-decomposablechemical foaming agent.
 4. The disc brake shim according to claim 1,wherein the disc brake shim is a base shim or a cover shim in alaminated shim in which the cover shim is laminated on the base shim. 5.A disc brake including pad materials on both sides in an axial directionof a disc rotor, and shims on opposite sides from the disc rotor, of thepad materials adjacently, wherein each of the shims is the disc brakeshim according to claim 1.